Towing in HOT temps

[RDEVans]

Hey all,

I have a 2010 Sierra 1500 AT Z71 with the 6.2. It has the max trailering package, 3.73 gear ratio. Believe it has the heavy duty oil and trans coolers. Towing a 5000-5500 travel trailer in 105-110 heat. Before I left I had all the fluids changed. First part of the trip it was cloudy, 70s/80s into low 90s and engine temp stayed locked at 210 and trans temp was running equal to air temp plus 90-100 (example air temp 85 trans temp 175-185). Second part of trip was very rolling. Air temps got up to 105-110 for about 6 hours while towing. Driving in 5th at 60-62 mph about 2000 rpms Engine temp would rise to 212-215 for the first 3-4 hours of the trip and trans ran 200-210. On bigger hills would climb to 215 then come back down after the crest. Towards the end of the trip after what I assumed was heat saturation the engine temp would hit 220 on a climb and transmission temp hit 216-217. The last little bit of the trip there was a very steep climb engine temp hit 220 and trans hit 230 right before the peak. Over the peak and on the way down trans was cooling back down. I kept it at 35-50 thru windy mountain roads last part of the trip which was another climb. Staying at those speeds the engine temp dropped to 210 but trans climbed into the 220s.

I was ok with the engine temp and expected that. Any concerns with the trans temp or was it ok because everything was just heat saturated and it would drop slowly on downhills? I tried to keep from shifting and bunting gears but should I have just gone to 4th and run at 2600-3000 rpm’s almost the whole time?

Thanks all.

 

[strutaeng]

Those temperatures are fine, especially since you say the peak temperatures go back down after cresting the hills/mountains.

You can always install a larger aftermarket transmission external cooler. Maybe consider lowering slightly the electric fans cut-in temperatures on the tune.

 

[OR VietVet]

Yes, install a larger transmission cooler and make double sure all of the cores are cleaned out for good air flow. Heat can and will radiate forward.

Is there a tow/haul mode on the transmission?

 

[PG01]

Hey all,

I have a 2010 Sierra 1500 AT Z71 with the 6.2. It has the max trailering package, 3.73 gear ratio. Believe it has the heavy duty oil and trans coolers. Towing a 5000-5500 travel trailer in 105-110 heat. Before I left I had all the fluids changed. First part of the trip it was cloudy, 70s/80s into low 90s and engine temp stayed locked at 210 and trans temp was running equal to air temp plus 90-100 (example air temp 85 trans temp 175-185). Second part of trip was very rolling. Air temps got up to 105-110 for about 6 hours while towing. Driving in 5th at 60-62 mph about 2000 rpms Engine temp would rise to 212-215 for the first 3-4 hours of the trip and trans ran 200-210. On bigger hills would climb to 215 then come back down after the crest. Towards the end of the trip after what I assumed was heat saturation the engine temp would hit 220 on a climb and transmission temp hit 216-217. The last little bit of the trip there was a very steep climb engine temp hit 220 and trans hit 230 right before the peak. Over the peak and on the way down trans was cooling back down. I kept it at 35-50 thru windy mountain roads last part of the trip which was another climb. Staying at those speeds the engine temp dropped to 210 but trans climbed into the 220s.

I was ok with the engine temp and expected that. Any concerns with the trans temp or was it ok because everything was just heat saturated and it would drop slowly on downhills? I tried to keep from shifting and bunting gears but should I have just gone to 4th and run at 2600-3000 rpm’s almost the whole time?

Thanks all.

I always liked these graphs…sorta sticks in the head

when you are done with your trip i would automatically change both fluids… engine oil and trans fluid. Or….if you are staying in one place for a while you can always have it done prior to returning home, then again when you get home, If you are worried. i believe finishing the trip and changing when home is fine. Id rather have fresh fluids than swapping a transmission.

 

[RDEVans]

Those temperatures are fine, especially since you say the peak temperatures go back down after cresting the hills/mountains.

You can always install a larger aftermarket transmission external cooler. Maybe consider lowering slightly the electric fans cut-in temperatures on the tune.

Thank you. Any recommendation on an aftermarket external trans cooler? Do most shops do tune work or is that someplace I just have to look up specific? I’ve never had anything done like that. Also considering moving up to a 3/4 ton truck. Would you suggest still doing the external cooler and tune? Thanks!

Yes, install a larger transmission cooler and make double sure all of the cores are cleaned out for good air flow. Heat can and will radiate forward.

Is there a tow/haul mode on the transmission?

Yes, I was in tow/haul mode. Suggestion for a cooler? Thanks!

 

[RDEVans]

I always liked these graphs…sorta sticks in the head View attachment 490188when you are done with your trip i would automatically change both fluids… engine oil and trans fluid. Or….if you are staying in one place for a while you can always have it done prior to returning home, then again when you get home, If you are worried. i believe finishing the trip and changing when home is fine. Id rather have fresh fluids than swapping a transmission.

Thanks for the charts. It should be cooler and generally downhill on the way home. Yes, will change fluids. Can you add an aftermarket oil temp pressure gauge? And I have heard that maybe GMc/ Chevy engine temp gauges are not the most accurate. Can you add a more accurate aftermarket temp gauge? Thanks!

 

[Foggy]

Keep it in 4th gear and let the 6.2 rpm up !!!!!
The hunting between 4th and 5th will cause high trans temps..
Just have to drive a bit slower. It's a lot easier on the trans in the long run.
I was thinking of going with 3.73 gears in 2014 to be able to tow in 5th gear
when flat.. but you already have that.... I wish there was a 3.90 gear made.
I don't want to give up too much mph with 4.10's when I'm not towing anything

 

[RDEVans]

Keep it in 4th gear and let the 6.2 rpm up !!!!!
The hunting between 4th and 5th will cause high trans temps..
Just have to drive a bit slower. It's a lot easier on the trans in the long run.
I was thinking of going with 3.73 gears in 2014 to be able to tow in 5th gear
when flat.. but you already have that.... I wish there was a 3.90 gear made.
I don't want to give up too much mph with 4.10's when I'm not towing anything

Thanks for the info! Yeah, wish a 3.90 was available!

 

[the blur]

You do know... well maybe not... GM has $10 zillion dollars into engineering these trucks.. I no longer tow, but when I did, it was with the factory tow package in all conditions. Steep grades, etc. Nothing ever blew up.

 

[j91z28d1]

You do know... well maybe not... GM has $10 zillion dollars into engineering these trucks.. I no longer tow, but when I did, it was with the factory tow package in all conditions. Steep grades, etc. Nothing ever blew up.

let's be fair, those zillion $ engineers designed the new 10 speeds and the new DI 6.2. both of which fail either within a few months if unlucky, and around around 100k if you're lucky. to the point last I heard they are completely moving onto the the 6.6L and giving up fixing the 6.2.

it's not much of a stretch at all to think our 15 plus year old trucks can use some cooling upgrades that gm didn't think was needed for the average driver to help with longevity. and definitely not unreasonable to want to do some upgrades at this point.


(cliff notes) gm is really really bad at building vehicles these days, and the newer the vehicle the worse it is.

 

[intheburbs]

I always liked these graphs…sorta sticks in the head View attachment 490188when you are done with your trip i would automatically change both fluids… engine oil and trans fluid. Or….if you are staying in one place for a while you can always have it done prior to returning home, then again when you get home, If you are worried. i believe finishing the trip and changing when home is fine. Id rather have fresh fluids than swapping a transmission.

Wow, did you really pull out "the chart?" Do you see the copyright date? 1999. Are you aware what advancements have been made since then? 1999 was right in the middle of mainstream usage of Dex 3.

That was 25 YEARS AGO.

Two big things have changed
1) Seals - all of the transmission manufacturers have switched to Viton (FKM) seals. Viton is rated for continuous service up to 400°. So the "Seals Harden" entry at 260° is utter BS.
2) Dex 6 has substantially better heat resistance than Dex 3. The "Trans Hot Idle Engine" warning only trips around 265°. The fluid itself doubles the oxidation resistance of Dex 3, and it's designed to pass GM's formal oxidation test - it runs the fluid at a constant 163 °C (325 °F) for 450 hours (with air injected).

 

[intheburbs]

I was ok with the engine temp and expected that. Any concerns with the trans temp or was it ok because everything was just heat saturated and it would drop slowly on downhills? I tried to keep from shifting and bunting gears but should I have just gone to 4th and run at 2600-3000 rpm’s almost the whole time?

Thanks all.

Yes, let the engine rev higher and lock it in 4th. Minimize shifting. Conversely, let it spin up on the way down, too, so you don't fry your brakes. On one descent, I was spinning the engine right up to 6000 RPM. Halfway down, the A/C stopped working. I figured I killed the compressor by spinning it so fast. Well, when we got all the way down, I pulled over and looked under the hood. The A/C belt was just dangling from the crank pulley. I spun it so fast it just stretched and walked off the pulley. I bought a new belt at an auto parts store and found a local mechanic to install it. He only wanted to charge me $50, but I insisted on giving him $100 because that's what it was worth to me. Two hours later we were back on the road with A/C.

I tow frequently in the Rockies with my Suburban. In fact we're heading there again soon, and we'll be scaling the usual spots - Eisenhower Tunnel - 11,100', and Powder River Pass - 9666'.

The Eisenhower approach might be the single, biggest "worst case scenario" for a tow vehicle. High altitude doesn't just mean thinner air and reduced cooling, it also means 30% less engine output. So my growling, snarling 6.0 LY6 rated at 364 hp is now wheezing to put out 255 hp. And it's trying to move 16,000 lbs. The western approach is about 12 miles of 7% grades before you reach the tunnel. The truck seems to find its sweet spot at 4000 RPM in 2nd gear doing 40 MPH. That sounds pathetic/slow, but I'm still faster than the big rigs and not blocking traffic.

 

[PG01]

Wow, did you really pull out "the chart?" Do you see the copyright date? 1999. Are you aware what advancements have been made since then? 1999 was right in the middle of mainstream usage of Dex 3.

That was 25 YEARS AGO.

Two big things have changed
1) Seals - all of the transmission manufacturers have switched to Viton (FKM) seals. Viton is rated for continuous service up to 400°. So the "Seals Harden" entry at 260° is utter BS.
2) Dex 6 has substantially better heat resistance than Dex 3. The "Trans Hot Idle Engine" warning only trips around 265°. The fluid itself doubles the oxidation resistance of Dex 3, and it's designed to pass GM's formal oxidation test - it runs the fluid at a constant 163 °C (325 °F) for 450 hours (with air injected).

Ummm, its a good guide?

 

[intheburbs]

Ummm, its a good guide?

If you're driving a 28 year-old car, I agree.

For the vehicles in the subforum, all running Dex6, you might as well be communicating via Morse code. It's out of date, and wrong.